In recent years, power generation systems which actuate generators using gas engines to generate electric power have been incorporated into facilities such as industrial plants. A power output of the gas engine is adjusted based on an intake-air pressure and a fuel amount, and the intake-air pressure is set higher and the fuel amount is set greater as a requested load is higher.
In general, the gas engine is supplied with a gas fuel from a fuel supply source provided by gas utilities, etc. The gas fuel supplied from the fuel supply source flows into the engine and is supplied to fuel feed valves provided to correspond to cylinders, respectively. The gas fuel is injected from each of the fuel feed valves to an inside of the cylinder or an intake port and is mixed with intake-air.
As described above, the gas fuel is injected against the intake-air. Therefore, the gas fuel cannot be injected properly, unless a pressure (hereinafter referred to as “gas engine inlet pressure”) of the gas fuel, which has flowed into the engine and is in a state which is immediately before being supplied to the fuel feed valve, is not higher than an intake-air pressure. If the gas engine inlet pressure is much higher than the intake-air pressure, a misfire occurs easily. Therefore, a differential pressure between the intake-air pressure and the gas engine inlet pressure is controlled to fall within a predetermined range (see Patent Literature 1).